function
<cfenv>

feclearexcept

int feclearexcept (int excepts);
Clear floating-point exceptions
Attempts to clear the floating-point exceptions specified by excepts.

Programs calling this function shall ensure that pragma FENV_ACCESS is enabled for the call.

Parameters

excepts
Bitmask value: A combination (with bitwise OR) of any number of floating-point exception values supported by the implementation:
macro valuedescription
FE_DIVBYZEROPole error: division by zero, or some other asymptotically infinite result (from finite arguments).
FE_INEXACTInexact: the result is not exact.
FE_INVALIDDomain error: At least one of the arguments is a value for which the function is not defined.
FE_OVERFLOWOverflow range error: The result is too large in magnitude to be represented as a value of the return type.
FE_UNDERFLOWUnderflow range error: The result is too small in magnitude to be represented as a value of the return type.
FE_ALL_EXCEPTAll exceptions (selects all of the exceptions supported by the implementation).
Certain library implementations may support additional floating-point exception values (with their corresponding macros also beginning with FE_).
Libraries may define in <fenv.h> only the macro values above they support (the others may not be defined).
At least all of the above macro values are defined in <cfenv> (even if not supported by the implementation).

Return Value

Zero, if all exceptions in excepts were successfully cleared (or if excepts was zero).
A non-zero value otherwise.

Example

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/* feclearexcept, fetestexcept example */
#include <stdio.h>      /* printf */
#include <math.h>       /* sqrt */
#include <fenv.h>       /* feclearexcept, fetestexcept, FE_ALL_EXCEPT, FE_INVALID */
#pragma STDC FENV_ACCESS on

int main ()
{
  feclearexcept (FE_ALL_EXCEPT);
  sqrt(-1);
  if (fetestexcept(FE_INVALID)) printf ("sqrt(-1) raises FE_INVALID\n");
  return 0;
}

Possible output:

sqrt(-1) raises FE_INVALID


Data races

Each thread maintains a separate floating-point environment with its own state. Spawning a new thread copies the current state. [This applies to C11 and C++11 implementations]

Exceptions

No-throw guarantee: this function never throws exceptions.
Note that C floating-point exceptions are not C++ exceptions, and thus are not caught by try/catch blocks.
Calling this function with pragma FENV_ACCESS off causes undefined behavior.

See also